Hydrostatically driven tractors have been around for many years and their application to windrowers has been significant. The tractor includes a tractor frame, a crop harvesting header mounted on the tractor frame for movement across the ground to harvest a standing crop, the header having a hydraulic motor for driving components of the header in the harvesting action, the tractor having two driven ground wheels each driven by hydraulic motor, a header control actuable by the driver, a first pump for generating a flow in a first pressurized hydraulic fluid for driving hydraulic motors of the ground wheels, a second pump for generating a flow in a second pressurized hydraulic fluid for driving the header motor, and an internal combustion engine on the tractor frame for driving the first and second pumps.
Recent developments in internal combustion engines have required what are known as “Tier Three” certified engines for EPA approval. It has been found that EPA Tier Three certified engines consume significantly more fuel than the Tier Two engines did, particularly at part load. This problem has been further compounded with increased fuel costs recently.
There are many patents by Caterpillar on engine control systems primarily used on earth moving equipment, and some are as follows:
U.S. Pat. No. 4,368,705 (Stevenson) issued Jan. 18, 1983 which discloses in relation to highway tractors the use of different timing maps of the fuel control to meet EPA standards, but does not relate to swather tractors which use different driving conditions;
U.S. Pat. No. 4,523,892 (Mitchell) issued Jun. 18, 1985 which is used in an excavator and which discloses controlling the hydraulic pump and the engine speed to reduce the pump displacement when the engine speed is lugged down.
U.S. Pat. No. 5,967,756 (Devier) issued Oct. 19, 1999 which discloses, in relation to an excavator, controlling the hydraulic pump and the engine speed to generate a required flow at best efficiency;
U.S. Pat. No. 7,017,674 (Bell) issued Mar. 28, 2006 which discloses changing the operating characteristics of an implement when attached to a tractor for use in different situations.
Also U.S. Pat. No. 6,199,006 (Weiss) issued Mar. 6, 2001 by Deere discloses reducing engine speed as a function of vehicle speed to avoid applying too much draw bar force at low speeds. This mentions engine performance maps.